Importing HD720 TGAs and losing color
Welcome to the forums.
You need to create a high-definition or a "Custom Settings" project with a resolution of 1280x720 with square pixels. You appear to be using a DV NTSC setting, which is why your frame size is restricted to 720x480.
The reason you're losing the background is likely because the TGA files have an alpha channel. You can use interpret footage to ignore the alpha channel, and thus make the background visible.
Search for the highlighted words in the PPro manual for more detail.
For DVD output, see: FAQ:What are the best settings for DVD?
You will also find links to many free tutorials in the PremiereProPedia that will quickly show you how things are done in Premiere Pro.